In steel shipbuilding, drains with internal trap, such as are shown in U.S. Pat. No. 558,569 by Sanders, U.S. Pat. No. 873,120 by Dunstan, U.S. Pat. No. 1,411,125 by O'Brian, U.S. Pat. No. 2,603,304 by Carrier, U.S. Pat. No. 3,042,210 by Hattori, U.S. Pat. No. 4,487,219 by Mäkelä et al, U.S. Pat. No. 4,922,948 by Van Dijk, and in particular U.S. Pat. No. 7,122,117 by Goldring et al are used because they are vertically more compact due to no p-trap requirement, and because these types of drains are more resistant to loss of trap seal resulting from listing of the ship. In U.S. Pat. No. 4,026,317, Ekstrom describes his trap drain as one which provides a “tortuous path” for the waste stream across multiple water seals, which each add resistance one to the next, resulting in greater absorption of pressure fluctuations while preserving seal integrity, as well as extending the time period in which an unused drain will lose seal due to evaporation. In U.S. Pat. No. 180,859 Falk talks about “widening and enlarging” the trap to oppose a larger volume of water to the sewer gases.
The aforementioned patents demonstrate the utility of the trap-in drain arrangement as well as the mechanism for reinforcing the trap seal through higher volume/mass of water against pressure fluctuations and as a means to increase trap seal endurance against evaporation. What is not found is a drain which incorporates trap-in-drain configuration along with adjustable height strainer and high-mass reinforced water seal.